The fermentation of carbohydrates to form butyl alcohol and acetone by Clostridium acetobutylicum (hereafter abbreviated C. acetobutylicum) was disclosed by Weizmann in U.S. Pat. No. 1,315,585. For many years, this process was used for the preparation of acetone and butyl alcohol, and a certain amount of ethyl alcohol was obtained as a by-product.
When the products from the acetone/butyl alcohol fermentation were fractionated, a high-boiling residue amounting to about 0.5 to 1.0% of the total yield of solvents remained in the stills. This was technically known as "yellow oil". Marvel and Broderick, J. Am. Chem. Soc., 47, 3045-3051 (1925), found that the "yellow oil" was a complex mixture of alcohols and esters. Saponification of this mixture and separation of the resulting products gave n-butyl alcohol as the largest alcoholic component of the hydrolyzate and butyric acid as the largest acidic component of the hydrolyzate. These results indicate that a very small amount of n-butyl butyrate is formed in the conventional acetone/butyl alcohol fermentation.
A fermentation process has now been discovered which surprisingly produces much higher yields of n-butyl butyrate. This product is useful as a component of flavors and fragrances and as a solvent.